The general rationale behind this proposed research is that circadian rhythm disturbances play important roles in insomnia and hypersomnia. The goal of the research proposed here is to further the understanding of sleep as a circadian phenomenon in Mus musculus. Our initial aims are: 1) to describe and compare the temporal distribution of wakefulness-sleep and acitivity-inactivity cycles in M. musculus under 12L-12D lighting conditions; 2) to describe and compare these distributions under DD constant conditions; 3) to describe and compare the influence of schedule and drug manipulations on such distributions. Data resulting from these studies will aid in the general understanding of wakefulness-sleep cycles and how they might come to be disrupted. Future work could build on such basic data and attempt to control the influence circadian rhythms have on pathological sleep.